Patellofemoral pain syndrome (PFPS) is a frequently encountered overuse disorder that involves the patellofemoral region and often presents as anterior knee pain. PFPS is the most common cause of knee pain seen by primary care physicians, orthopedic surgeons, and sports medicine specialists [1,2]. PFPS can be difficult to diagnose. Not only do the etiology, diagnosis, and treatment remain challenging, but the terminology used to describe PFPS is used inconsistently and can be confusing. The terms patellofemoral joint syndrome and chondromalacia patellae are also used to describe this condition.

Patellofemoral pain syndrome (PFPS) can be defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peripatellar pathology. PFPS describes a symptom complex and is a diagnosis of exclusion.

Common synonymous terms include retropatellar pain syndrome, runner's knee, lateral facet compression syndrome, and idiopathic anterior knee pain. The term chondromalacia patella is used to describe pathologic changes in the articular cartilage of the patella, such as softening, erosion, and fragmentation. While frequently confused with PFPS, chondromalacia patella is a pathologic diagnosis and constitutes a distinct cause of knee pain [3].

EPIDEMIOLOGY

Patellofemoral pain syndrome (PFPS) is among the most common diagnoses in sports medicine. Although PFPS is often seen in active individuals and may account for 25 to 40 percent of all knee problems seen in a sports injury clinic, the true incidence is not known [4]. PFPS affects many running athletes and constitutes nearly 25 percent of all identified knee injuries [5-7]. (See "Overview of running injuries of the lower extremity".)

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